McIlroy’s eagerness to get going was written all over his social media accounts. On Instagram he posted his muscled self-bench pressing 275lb, while on Twitter he said “excited is an understatement”.

Just to raise the pulse further, on the first tee were his Claret Jug and his Wanamaker Trophy.

McIlroy went through the first five holes in four under. “I should have birdied the third as well,” he said. His partner, Henrik Stenson, was shaking his head, however. “Wasn’t much rust, was there?” the defending champion said.

On the par-four first, McIlroy hit a driver, an eight iron to 12 feet. On the par-five second, he hit a driver, three-iron and two-putted from 30 feet. Then came the “disastrous” par-four third where he missed from six feet. But he bounced back with a three-iron to four feet on the par-three fourth and a lob wedge to five feet on the par-five fourth.

Anything seemed possible at that point, but although his general play kept on the boil, his putter cooled off. “I didn’t hole as many as I could have but it still added up to six under and I’m happy,” he said.

As the field is redrawn for the second round, McIlroy goes out with joint leader Shane Lowry, who is also his oldest friend on tour.

The pair played together in the Irish amateur team when they were teens and remain close despite Lowry still being managed by Conor Ridge’s Horizon agency, with which McIlroy is involved in a bitter legal battle.

While McIlroy has one eye on next year’s Masters – where he will attempt to win his third major in a row as well as becoming the sixth player in history to complete the career Grand Slam – his big pal from county Offaly is finding it increasingly tortuous having both eyes on Augusta.

The 27-year-old is 52nd in the world, with the top 50 in the rankings at the end of the year qualifying for the season’s first major. A top-13 finish would haul him inside the top 50, but if he wants to be certain of a Masters debut, Lowry – who famously won the Irish Open as an amateur – knows that he needs to finish deep inside the top 10.

“It’s been playing on my mind,” Lowry said, admitting that the pressure might have been a factor in last Sunday’s collapse at the Turkish Airlines Open, when he crashed to 25th after holding the lead with 14 holes remaining. “I am sick of talking about it [the Masters], I am sick of thinking about it. But I am just going to have to deal with it and play well.”

Lowry and McIlroy are one ahead of Scotland’s Richie Ramsay and the Dane Thorbjorn Olesen with Stenson and Argentina’s Emiliano Grillo a further stroke back.

Meanwhile, Matt Fitzpatrick, the former US Amateur champion, claimed one of the 25 European Tour cards on offer at qualifying school in Catalunya. The 20-year-old from Sheffield shot a 68 in the last of six rounds to finish on 10 under and inside the top 10. But the most remarkable showing came from Italian 17-year-old Renato Paratore who, on 16 under, came third behind Finn Mikko Korhonen.